-Added MergeNullValueHandling

Src/Newtonsoft.Json.Tests/Linq/MergeTests.cs

@@ -569,5 +569,36 @@ namespace Newtonsoft.Json.Tests.Linq
             Assert.AreEqual("name1", p.Name);
             Assert.AreEqual(0, p.Count);
         }
+
+        [Test]
+        public void MergeNullValue()
+        {
+            var source = new JObject
+            {
+                {"Property1", "value"},
+                {"Property2", new JObject()},
+                {"Property3", JValue.CreateNull()},
+                {"Property4", JValue.CreateUndefined()},
+                {"Property5", new JArray()}
+            };
+
+            var patch = JObject.Parse("{Property1: null, Property2: null, Property3: null, Property4: null, Property5: null}");
+
+            source.Merge(patch, new JsonMergeSettings
+            {
+                MergeNullValueHandling = MergeNullValueHandling.Merge
+            });
+
+            Assert.IsNotNull(source["Property1"]);
+            Assert.AreEqual(JTokenType.Null, source["Property1"].Type);
+            Assert.IsNotNull(source["Property2"]);
+            Assert.AreEqual(JTokenType.Null, source["Property2"].Type);
+            Assert.IsNotNull(source["Property3"]);
+            Assert.AreEqual(JTokenType.Null, source["Property3"].Type);
+            Assert.IsNotNull(source["Property4"]);
+            Assert.AreEqual(JTokenType.Null, source["Property4"].Type);
+            Assert.IsNotNull(source["Property5"]);
+            Assert.AreEqual(JTokenType.Null, source["Property5"].Type);
+        }
     }
 }

Src/Newtonsoft.Json/Linq/JObject.cs

@@ -187,7 +187,7 @@ namespace Newtonsoft.Json.Linq
                     JContainer existingContainer = existingProperty.Value as JContainer;
                     if (existingContainer == null)
                     {
-                        if (contentItem.Value.Type != JTokenType.Null)
+                        if (contentItem.Value.Type != JTokenType.Null || settings?.MergeNullValueHandling == MergeNullValueHandling.Merge)
                         {
                             existingProperty.Value = contentItem.Value;
                         }

Src/Newtonsoft.Json/Linq/JsonMergeSettings.cs

@@ -8,6 +8,7 @@ namespace Newtonsoft.Json.Linq
     public class JsonMergeSettings
     {
         private MergeArrayHandling _mergeArrayHandling;
+        private MergeNullValueHandling _mergeNullValueHandling;
 
         /// <summary>
         /// Gets or sets the method used when merging JSON arrays.
@@ -26,5 +27,23 @@ namespace Newtonsoft.Json.Linq
                 _mergeArrayHandling = value;
             }
         }
+
+        /// <summary>
+        /// Gets or sets how how null value properties are merged.
+        /// </summary>
+        /// <value>How null value properties are merged.</value>
+        public MergeNullValueHandling MergeNullValueHandling
+        {
+            get { return _mergeNullValueHandling; }
+            set
+            {
+                if (value < MergeNullValueHandling.Ignore || value > MergeNullValueHandling.Merge)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(value));
+                }
+
+                _mergeNullValueHandling = value;
+            }
+        }
     }
 }

Src/Newtonsoft.Json/Linq/MergeNullValueHandling.cs

@@ -0,0 +1,21 @@
+using System;
+
+namespace Newtonsoft.Json.Linq
+{
+    /// <summary>
+    /// Specifies how null value properties are merged.
+    /// </summary>
+    [Flags]
+    public enum MergeNullValueHandling
+    {
+        /// <summary>
+        /// The content's null value properties will be ignored during merging.
+        /// </summary>
+        Ignore = 0,
+
+        /// <summary>
+        /// The content's null value properties will be merged.
+        /// </summary>
+        Merge = 1
+    }
+}

Src/Newtonsoft.Json/Newtonsoft.Json.Net20.csproj

@@ -125,6 +125,7 @@
     <Compile Include="Linq\JsonPath\QueryFilter.cs" />
     <Compile Include="Linq\JsonPath\ScanFilter.cs" />
     <Compile Include="Linq\MergeArrayHandling.cs" />
+    <Compile Include="Linq\MergeNullValueHandling.cs" />
     <Compile Include="MetadataPropertyHandling.cs" />
     <Compile Include="SerializationBinder.cs" />
     <Compile Include="Serialization\DiagnosticsTraceWriter.cs" />

Src/Newtonsoft.Json/Newtonsoft.Json.Net35.csproj

@@ -139,6 +139,7 @@
     <Compile Include="Linq\JsonPath\QueryFilter.cs" />
     <Compile Include="Linq\JsonPath\ScanFilter.cs" />
     <Compile Include="Linq\MergeArrayHandling.cs" />
+    <Compile Include="Linq\MergeNullValueHandling.cs" />
     <Compile Include="MetadataPropertyHandling.cs" />
     <Compile Include="SerializationBinder.cs" />
     <Compile Include="Serialization\DiagnosticsTraceWriter.cs" />

Src/Newtonsoft.Json/Newtonsoft.Json.Net40.csproj

@@ -139,6 +139,7 @@
     <Compile Include="Linq\JsonPath\QueryFilter.cs" />
     <Compile Include="Linq\JsonPath\ScanFilter.cs" />
     <Compile Include="Linq\MergeArrayHandling.cs" />
+    <Compile Include="Linq\MergeNullValueHandling.cs" />
     <Compile Include="MetadataPropertyHandling.cs" />
     <Compile Include="Serialization\DiagnosticsTraceWriter.cs" />
     <Compile Include="Serialization\ExpressionValueProvider.cs" />

Src/Newtonsoft.Json/Newtonsoft.Json.Portable.csproj

@@ -136,6 +136,7 @@
     <Compile Include="Linq\JTokenWriter.cs" />
     <Compile Include="Linq\JValue.cs" />
     <Compile Include="Linq\MergeArrayHandling.cs" />
+    <Compile Include="Linq\MergeNullValueHandling.cs" />
     <Compile Include="MemberSerialization.cs" />
     <Compile Include="MetadataPropertyHandling.cs" />
     <Compile Include="MissingMemberHandling.cs" />

Src/Newtonsoft.Json/Newtonsoft.Json.Portable40.csproj

@@ -141,6 +141,7 @@
     <Compile Include="Linq\JTokenWriter.cs" />
     <Compile Include="Linq\JValue.cs" />
     <Compile Include="Linq\MergeArrayHandling.cs" />
+    <Compile Include="Linq\MergeNullValueHandling.cs" />
     <Compile Include="MemberSerialization.cs" />
     <Compile Include="MetadataPropertyHandling.cs" />
     <Compile Include="MissingMemberHandling.cs" />

Src/Newtonsoft.Json/Newtonsoft.Json.csproj

@@ -140,6 +140,7 @@
     <Compile Include="Linq\JValue.cs" />
     <Compile Include="Linq\JsonLoadSettings.cs" />
     <Compile Include="Linq\MergeArrayHandling.cs" />
+    <Compile Include="Linq\MergeNullValueHandling.cs" />
     <Compile Include="MemberSerialization.cs" />
     <Compile Include="MetadataPropertyHandling.cs" />
     <Compile Include="MissingMemberHandling.cs" />